Refactor SSH config to use host-specific keys and disable nix

- Convert SSH config to template with @SSH_KEY@ placeholder
- Add sshKey field to host configurations (mac14, ordio)
- Update home.nix to dynamically substitute SSH keys per host
- Change docker cask to docker-desktop in cask.nix
- Add development packages to ordio host (mkcert, dnsmasq, etc.)
- Disable nix in darwin.nix configuration

home/home.nix

@@ -33,7 +33,9 @@
       ".config/nvim".source = ../files/nvim;
 
       # Secrets
-      ".ssh/config".source = ../secrets/ssh/config;
+      ".ssh/config".text = builtins.replaceStrings [ "@SSH_KEY@" ] [ host.sshKey ] (
+        builtins.readFile ../secrets/ssh/config.template
+      );
     };
 
     shellAliases = {